Tile Calculator: How Many Tiles Do I Need?

How to measure for tile

1. Measure the length and width of the area. For a floor, go wall to wall. For a wall or backsplash, measure the width and the height you plan to tile.
2. Break odd shapes into rectangles. Measure each section, work out its area, and add them together. Our square footage calculator adds up to three areas for you. Then enter the total as a length with a width of 1.
3. Subtract what will not be tiled. Leave out cabinet footprints on a floor, and windows, niches, or the space behind a range on a wall, if they are large.
4. Measure a tile. Use the listed size in inches, such as 12 x 24. The calculator converts it to square feet.
5. Check the box. Note how many tiles come in each box. The calculator rounds up to whole boxes. Carpet comes off a roll instead; see the carpet calculator.
6. Choose the extra. Use the table below to pick a percentage for your layout and room shape.

Tiles needed by tile size

This chart shows how tile size changes the count. The last two columns use the calculator's formula for the default 8 x 10 ft floor.

A 12 x 12 and a 6 x 24 tile cover the same area, so they need the same count. The plank shape can still waste more in practice, because long tiles can leave long offcuts at the walls. For laminate or vinyl plank, use the flooring calculator.

Quick answers: floors, a tub surround, a shower, and a backsplash

Each row is an example size worked with the calculator's formula and 10 percent extra for a straight layout. For walls, the area is the width times the height you tile.

The tub row uses the most common alcove tub, about 60 in long and 30 in wide according to The Home Depot's bathtub buying guide: a 5 x 6 ft back wall (30 sq ft) plus two 2.5 x 6 ft end walls (15 sq ft each). The International Residential Code, section R307.2, requires the walls above a tub with a shower head, and the walls of a shower compartment, to have a nonabsorbent surface at least 6 ft above the floor. Tiling 6 ft above the tub rim, as in the example, clears that height; tiling to the ceiling takes more.

Boxes of tile by room size and box coverage

9 boxes of 10 sq ft for an 8 x 10 ft floor with 10 percent extra: boxes = square feet with the extra, divided by the square feet printed on the box, rounded up. Box coverage differs from one tile to the next, so read it on the carton. With 10 percent extra:

The calculator asks for tiles per box instead: divide the box's square feet by the square feet of one tile. A 16 sq ft box of 12 x 24 in tile holds 8 tiles, and for a 10 x 10 ft floor the calculator then shows "You need 55 tiles (7 boxes)." For a diagonal or patterned layout, use the larger extra from the next section.

Large tile: offsets and grout joints

Big tiles look simple, but industry standards add a few rules that affect the layout, and the layout affects waste.

Keep offsets at 33 percent or less

The Ceramic Tile Foundation explains that under ANSI A108.02, when any side of the tile is longer than 15 in, a running bond offset should be no more than 33 percent unless the tile manufacturer says otherwise. Large tiles can have some edge warpage, and a 50 percent offset puts the center of one tile beside the ends of its neighbors, where any height difference (lippage) shows most. A one-third offset changes where your cut pieces fall, so plan your rows before you buy.

Grout joints

The Tile Council of North America notes that ANSI A108.02 requires grout joints at least three times the actual size variation of the tiles supplied, and advises avoiding patterns that put the center of one large tile near the end of another when you use a narrow grout joint. For running bond with any tile side over 15 in, the Ceramic Tile Foundation cites ANSI minimums of 1/8 in for rectified tile and 3/16 in for calibrated tile, widened by the amount of edge warpage. To size the grout, use the grout calculator.

Mortar: how many bags of thinset

Tile count is only half the shopping list. Thinset coverage depends heavily on the trowel notch, and the deeper the notch, the fewer square feet a bag covers. Here is what three manufacturers list for a 50 lb bag: Custom Building Products for VersaBond Professional, LATICRETE for 253 Gold, and MAPEI for Ultraflex LHT, its large-and-heavy-tile mortar. The bag counts use the lowest figure in each row:

For the default 80 sq ft floor, VersaBond's figures give one bag with the smallest notch but two bags with the 1/2 in notch. For the trowel, MAPEI's rule of thumb is a 1/2 x 1/2 x 1/2 in square notch for large format tile, with any side longer than 15 in, and a 1/4 x 1/4 x 1/4 in or 1/4 x 3/8 x 1/4 in square notch for smaller tile. Use the trowel size your tile and mortar instructions call for, and check the coverage on the bag you actually buy, since products differ.

Tile floor thickness: tile, mortar, and underlayment

3/4 in above the subfloor for 5/16 in tile on 1/4 in cement board with the thinnest mortar beds. Add the layers: the tile, the mortar under it, and any underlayment with its own mortar bed. Schluter calls 5/16 in a typical tile thickness. Custom Building Products puts the mortar between tile and substrate at a minimum of 3/32 in and a maximum of 1/4 in for mortars without an ANSI "H" rating. James Hardie uses its 1/4 in HardieBacker cement board on wood floors, set in a bed of thinset spread with a 1/4 in square-notch trowel, and Schluter's DITRA membrane is 1/8 in thick. With 5/16 in tile, and the mortar under the board or membrane counted at the same 3/32 to 1/4 in:

Large and heavy tile can sit on a thicker bed: VersaBond Professional can be applied 1/2 in thick on horizontal surfaces, and MAPEI lists 3/32 to 1/2 in for Ultraflex LHT. Check your tile's own thickness on the box or spec sheet. The subfloor itself is extra: James Hardie asks for at least 5/8 in exterior plywood or 23/32 in OSB under the board.

Tips and common mistakes

• Buying everything at once. Clé Tile recommends buying all your tile, including the extra, together so it comes from the same production run. Tile bought later can differ in color.
• Forgetting trim pieces. Bullnose, pencil liners, and edge trims are sold separately. Count them by the linear foot of exposed edge and check the length of each piece. For trim that runs around a whole room, the baseboard calculator turns its length and width into linear feet and pieces.
• Using the wrong extra for the layout. A herringbone or diagonal floor at 10 percent is an easy way to run short.
• Ignoring the box count. Tile is sold by the box, so the calculator rounds up. Look at how many spare tiles that leaves; if it is only one or two on a diagonal job, consider one more box.
• Not planning the edges. Dry-lay a row or sketch the layout so you do not end with thin slivers at a wall or doorway. Centering the layout can use more cuts, so settle it before you order.
• Throwing out the spares. Keep a few tiles and write the room on the box. Discontinued tile is almost impossible to match later.